The fattest female teacher in every school who makes class entertaining by her comedic weight, but whom is completely unaware of the numerous jokes which occur reguarding her gargantuan size each lesson.

May also be a Bulgarian shot putter.

For example, in mathematics:
*Hannah calls Big Berta for help on a question*
Big Bertha then bends over to help Hannah with her problem. Upon noticing this, Jack calls to Boris and says "Boris, Hannah wants you," causing the unsuspecting Boris to look in the direction of Big Bertha's arse in its entirety. This is then rounded off with the majority of the class shouting "Whaaaaaay!" accompanied with many "wanker" hand gestures, leaving Boris feeling extremely stupid and traumatised by his experience.